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LibJS: Implement String.prototype.substring with UTF-16 code units

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Timothy Flynn 2021-07-19 13:15:30 -04:00 • committed by Andreas Kling
parent 767700d8a1
commit 60d8852fc2
2 changed files with 23 additions and 21 deletions
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33
Userland/Libraries/LibJS/Runtime/StringPrototype.cpp
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@ -497,40 +497,31 @@ JS_DEFINE_NATIVE_FUNCTION(StringPrototype::concat)
// 22.1.3.23 String.prototype.substring ( start, end ), https://tc39.es/ecma262/#sec-string.prototype.substring // 22.1.3.23 String.prototype.substring ( start, end ), https://tc39.es/ecma262/#sec-string.prototype.substring
JS_DEFINE_NATIVE_FUNCTION(StringPrototype::substring) JS_DEFINE_NATIVE_FUNCTION(StringPrototype::substring)
{ {
auto string = ak_string_from(vm, global_object); auto string = utf16_string_from(vm, global_object);
if (!string.has_value()) if (vm.exception())
return {}; return {};
if (vm.argument_count() == 0)
return js_string(vm, *string);
// FIXME: index_start and index_end should index a UTF-16 code_point view of the string. Utf16View utf16_string_view { string };
auto string_length = string->length(); auto string_length = static_cast<double>(utf16_string_view.length_in_code_units());
auto start = vm.argument(0).to_integer_or_infinity(global_object); auto start = vm.argument(0).to_integer_or_infinity(global_object);
if (vm.exception()) if (vm.exception())
return {}; return {};
auto end = (double)string_length;
auto end = string_length;
if (!vm.argument(1).is_undefined()) { if (!vm.argument(1).is_undefined()) {
end = vm.argument(1).to_integer_or_infinity(global_object); end = vm.argument(1).to_integer_or_infinity(global_object);
if (vm.exception()) if (vm.exception())
return {}; return {};
} }
size_t index_start = clamp(start, static_cast<double>(0), static_cast<double>(string_length));
size_t index_end = clamp(end, static_cast<double>(0), static_cast<double>(string_length));
if (index_start == index_end) size_t final_start = clamp(start, static_cast<double>(0), string_length);
return js_string(vm, String("")); size_t final_end = clamp(end, static_cast<double>(0), string_length);
if (index_start > index_end) { size_t from = min(final_start, final_end);
if (vm.argument_count() == 1) size_t to = max(final_start, final_end);
return js_string(vm, String(""));
auto temp_index_start = index_start;
index_start = index_end;
index_end = temp_index_start;
}
auto part_length = index_end - index_start; return js_string(vm, utf16_string_view.substring_view(from, to - from));
auto string_part = string->substring(index_start, part_length);
return js_string(vm, string_part);
} }
// B.2.3.1 String.prototype.substr ( start, length ), https://tc39.es/ecma262/#sec-string.prototype.substr // B.2.3.1 String.prototype.substr ( start, length ), https://tc39.es/ecma262/#sec-string.prototype.substr

11
Userland/Libraries/LibJS/Tests/builtins/String/String.prototype.substring.js
View file

@ -12,3 +12,14 @@ test("basic functionality", () => {
expect("hello friends".substring(0, "5")).toBe("hello"); expect("hello friends".substring(0, "5")).toBe("hello");
expect("hello friends".substring("6", "13")).toBe("friends"); expect("hello friends".substring("6", "13")).toBe("friends");
}); });
test("UTF-16", () => {
var s = "😀";
expect(s).toHaveLength(2);
expect(s.substring()).toBe("😀");
expect(s.substring(0)).toBe("😀");
expect(s.substring(0, 2)).toBe("😀");
expect(s.substring(0, 1)).toBe("\ud83d");
expect(s.substring(1, 2)).toBe("\ude00");
expect(s.substring(2, 2)).toBe("");
});